Active carbon



May 24. 1966 Q G, B1GELOW, JR, ET AL 3,252,919

ACTIVE CARBON Filed March 25, 1963 FIG. 2

5 msm cya THEORETICAL COMBUSTION AIR NVENTORS, CHARLES G. BlGELOW JR BYWlLLAM W. HASSLLER ATTORNEYA United States Patent O 3,252,919 ACTIVE CARBON Charles G. Bigelow, Jr., Wayne, and William W. Hassler, Willow Grove, Pa., assignors to Selas Corporation of America, Dresher, Pa., a corporation of Pennsylvania Filed Mar. 25, 1963, Ser. No. 267,617 7 Claims. (Cl. 252-421) The present invention relates to `active carbon, and more particularly to a method of making the material.

At the present time most active carbon is made by a process in which the carbonaceous material is rst charred, and the charred material is then chemically treated to make it active. This two-step process produces an active carbon that is suited for particular purposes depending upon the particular chemical that is used to make it active. i

It is an object of the present invention to provide a simple, one-step method of manufacturing active carbon.

In practicing the invention, the material to be treated is placed in a sealed chamber and heated to a temperature where it will be charred in an atmosphere of products of combustion that have a deficiency of air, and therefore are rich in unburned combustibles. The material is then cooled in a nonoxidizing atmosphere.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the `accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a diagrammatic view of apparatus in which the method can be carried out, and

FlG. 2 contains curves showing ranges of conditions in which the process may be carried out.

ln FIG. 1 of the drawing there is shown one form of apparatus in which the invention can be carried out. The apparatus includes a furnace 1 having a chamber 2 in which the material to be treated is heated. This chamber is provided with an entrance closed by a door 3 that can be operated in any suitable manner as by a cable 4. The chamber is also provided with an exit that connects with a cooling chamber 5 and is separated therefrom by a door 6 that may be operated by a cable 7. The cooling chamber has an exit that is closed by a door 8 which can be operated by a cable 9. The structures forming the furnace and cooling chamber are constructed so that they are substantially air tight, thereby permitting a desired atmosphere to be kept in them.

Furnace chamber 2 is heated by one or more burners 11 like those disclosed in Hess application Serial No. 154,455 tiled November 24, 1961. These burners are supplied with fuel and air through pipes 12 and 13, respectively; the ratios of fuel and air being adjusted to a desired value by an ordinary ratio controller 14. A portion of the products of combustion are withdrawn through the burner and burned therein with additional air supplied through a pipe 15 to preheat the air. Products of combustion are discharged through an exhaust 16 in amounts adjusted by the aspirating effect of a jet of air from pipe 17.

A nonoxidizing atmosphere is maintained in cooling chamber 5. One convenient way to accomplish this is to pass atmosphere from furnace chamber 2 through a duct 18 and a gas cooler 19 to the cooling chamber. It will be obvious, however, that the proper atmosphere can be provided from any other source.

In using the apparatus to carry out the method of the invention, carbonaceous material 21, to be treated, is

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loaded on or in a suitable carrier 22 and moved into the furnace chamber. The material, which may be small blocks of wood, sawdust, ground ooal or other carbonaceous material that can be charred, is so arranged on the carrier that the surfaces of the material can be contacted by the furnace atmosphere that is being circulated through the chamber.

Burner 11 is supplied with a gas fuel and air in such proportions that there is a deficiency of theoretical corubustion air, thereby producing a rich fuel mixture burning in furnace chamber 2 with no free oxygen in the products of combustion. If, for example, the gas used is such that an air-gas ratio of 8.5 to 1 is required for a stoichiometric mixture, or 100% of theoretical air, the ratio supplied to the burner will be from about 6 to 1 to about 7.3 to l. With these ratios in addition to the normal products of combustion including water vapor and CO2, there will be a deciency of air from the amount theoretically required of from 30% to 15% and there will be from 16.5% to 8.2% of the original supply of gas unburned in the chamber. With such an air-gas ratio it would be dicult to obtain combustion and the temperatures required for the process. A portion of the products of combustion, including the unburned gas, is removed from the furnace chamber through burner 11 and burned in a chamber therein with additional air supplied through pipe 15 to preheat the air supplied to the burner, as explained in the above mentioned application.

Burner 11 is fired at such a rate that the furnace temerature is normally kept between 1550 F. and 1700 F. When the furnace is at substantially the desired temperature the material to be treated is moved into the chamber and kept there for from 5 minutes to 2 hours, depending upon the size of the pieces and their composition. Generally speaking, it is advisable to increase the percentage of unburned gas or reduce the percent of theoretical combustion air as the temperature of the furnace is raised. Such a relation is shown in the curves of FIG. 2. lf the percentage of theoretical combustion air is kept Within values between lines a and b for a given temperature, satisfactory active carbon will be produced. At the end of the heating time door 6 is opened and the treated material is moved by its carrier 22 into cooling chamber 5 and door 6 closed. The cooling chamber has the same atmosphere as that in the furnace chamber, or any other nonoxidizing atmosphere, so that the surface of the treated material will not be oxidized as the material is being cooled to or near r-oom temperature. When the material is cooled enough so that it will not oxidize in the air it can be removed from chamber 5. One batch of material can be heated as another is being cooled, so that, with the equipment shown, the process is semicontinuous.

As an example of the process, one inch cubes of a dry, soft pine wood were heated at l700 F. in a furnace for about one hour. The furnace was supplied with an air' gas ratio of 6.2 to 1, which resulted in 28% deficiency of theoretical combustion air and about 14.4% combustibles in the furnace atmosphere. After heating, the wood was cooled in a nonoxidizing atmosphere. Standard molasses tests on the product indicated 88% to 92% color removal. The material so produced was found to 'have superior decolorizing properties and at least average gas adsorption properties.

The exact reason why the process produces such excellent results is not entirely understood. lt is believed, however, that the high adsorptive power of the wood charcoal is probably the result of an optimum concentration and ratio of oxidizing agents (H2O and CO2) in the furnace atmosphere so as to oxidize the carbon surface at a slow rate which enables the activating gases to act completely on the unactivated material. It is also believed that the unburned gas in the furnace chamber singly or in combination with the other gases exerts a beneficial catalytic eifect. In any event, the carbonaceous material is charred and activated in the single step of heating it as described in the presence of unburned gas and products of combustion, with the heating requiring only a relatively short time.

While in accordance with the provisions of the statutes we have illustrated and described the best form of embodiment of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed Without departing from the spirit and scope of the invention set forth in the appended claims, and that in some cases certain features of our invention may be used to advantage without a corresponding use of other features.

What is claimed is:

1. The method of making active carbon which comprises placing uncharred particles of a carbonaceous material that can be charred in an enclosure, heating said material to a temperature from about 15.50 F. to 1700 F. for a period of time of from 5 minutes to 2 hours in direct contact with an atmosphere of products of combustion that are rich in unburned hydrocarbon fuel and no free oxygen, said products being produced by direct cornbustion of hydrocarbon fuel and air in said enclosure, circulating the atmosphere around the material during heating, and cooling the material in a nonoxidizing atmosphere to a temperature below which it will oxidize in the air.

2. The method of making active charcoal which comprises placing uncharred carbonaceous material that can be charred in a closed chamber and heating it in said chamber to a temperature between about 1550 F. and about 1700 F. for a period of time between 5 minutes and 2 hours, accomplishing said heating by tiring a burner directly in said chamber to obtain direct contact between said carbonaceous material and hot products of combustion, and supplying the burner with fuel and air mixture having of theoretical combustion air deciency of 40 from 15% to 30%.

3. The method of claim 2 in which said carbonaceous material is in the form of small pieces of wood.

4. The method of claim 3 in which said carbonaceous material is heated for about one hour at about 1700 F;

5. The method of claim 4 in which the products of combustion surrounding the carbonaceous material result from the burning of a fuel air mixture having a theoretical combustion air deficiency of about 28% 6. The method of making active carbon which comprises placing' small pieces of an uncharred carbonaceous material that can be charred in an enclosed chamber, burning directly in said chamber a rich mixture of gas and air to heat said pieces of material to between about 1550 F. and 1700 F. in an atmosphere of products of combustion and unburned gas for from about 5 minutes to two hours, the products of combustion from the burning circulating freely about the material while it is being heated in the chamber and cooling said material substantially to atmosphere temperature in a nonoxidizing atmosphere.

7. The method of claim 6 in which said material is cooled in a chamber separate from the one in which it was heated, and thecooling atmosphere used in the second chamber is atmosphere removed from the chamber in which the material was heated.

References Cited by the Examiner UNITED STATES PATENTS 1,591,235 7/1926 Rodman 252--445 1,753,984 4/ 1930 Enssle 252-445 1,774,585 9/1930 Barnebey 252-421 2,643,182 6/1953 Williams 252-445 X 3,011,981 12/1961 Soltes 252-421 FOREIGN PATENTS 136,873 12/1919 Great Britain,

273,761 9/ 1928 Great Britain.

446,505 4/ 1936 Great Britain.

546,531 7/1942 Great Britain.

BENJAMIN HENKIN, Primary Examiner.

MAURICE A. BRINDISI, Examiner.

R. D. EDMUNDS, H. S. MILLER, Assistant Examiners. 

1. THE METHOD OF MAKING ACTIVE CARBON WHICH COMPRISES PLACING UNCHARRED PARTICLES OF A CARBONACEOUS MATERIAL THAT CAN BE CHARRED IN AN ENCLOSURE, HEATING SAID MATERIAL TO A TEMPERATURE FROM ABOUT 1550*F. TO 1700* F. FOR A PERIOD OF TIME OF FROM 5 MINUTES TO 2 HOURS IN DIRECT CONTACT WITH AN ATOMOSPHERE OF PRODUCTS OF COMBUSTION THAT ARE RICH IN UNBURNED HYDROCARBON FUEL AND NO FREE OXYGEN, SAID PRODUCTS BEING PRODUCED BY DIRECT COMBUSTION OF HYDROCARBON FUEL AND AIR IN SAID ENCLOSURE CIRCULATING THE ATMOSPHERE AROUND THE MATERIAL DURING HEATING, AND COOLING THE MATERIAL IN A NONOXIDIZING ATMOSPHERE TO A TEMPERATURE BELOW IT WILL OXIDIZE IN THE AIR. 